ACJC H1 CHEM P2 Prelim

1 Centre Number Index Number Name and Class ANGLO-CHINESE JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Advanced Level CHEMISTRY 8872/02 Higher 1 Paper 2 Structured & Free Response 24th August 2009 2 hour Candidates answer on the Question Paper & Writing Paper Additional Materials: Data Booklet Writing Paper String READ THESE INSTRUCTIONS FIRST Write your name, Centre number and index number on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in Section A & answer 2 out of 3 questions in Section B A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together including the cover page. For Examiner's Use Question no. Marks 1 2 3 Section A 4 Section B (2 out of 3) Total This document consists of 10 printed pages. ACJC 2009 8872/02/Aug/09 Preliminary Examination

2 Section A Answer all questions in the spaces provided on the question paper. 1 Carbonyl chloride, COCl 2 (structure as shown below), exists as a toxic gas which reacts rapidly with water to evolve two different acidic gases. C O ClCl (a) (i) The reaction of carbonyl chloride with water is found to proceed via the reaction pathway as shown below: C O ClCl Name the reaction that has occurred to produce the intermediate A. [1] (b) An unknown amount of carbonyl chloride was reacted with water (in excess). COCl 2 + H2O → 2HCl + CO2 The two acidic gases required 25.0cm 3 of 0.100mol dm -3 o f N a O H f o r complete neutralization. (i) Calculate the amount of NaOH that has reacted. [1] (ii) Given that complete neutralization occurs for the two gases, write two equations to show the reactions of NaOH with HCl and NaOH with CO 2 respectively. [2] HCl + CO2 Intermediate A Intermediate B C OH HO Cl Cl C O ClHO ACJC 2009 8872/02/Aug/09 Preliminary Examination

3 (iii) Using your answers in (ii), calculate the volume of HCl evolved at room temperature and pressure given that 1 mol of a gas occupies a volume of 24 dm3 under room temperature and pressure. [1] (c) (i) Chlorine has an oxidation state of -1 in HCl. State the oxidation states of chlorine in ClO - and ClO3 -. [2] (ii) ClO -, hypochlorite, is a powerful oxidizing agent and is used commonly in household bleaches. Write a balanced redox reaction between ClO - and I - in an acidic medium given that ClO - is converted to Cl - at the end of reaction. [2] [10 marks] 2 (a) When the hydrocarbon with the molecular formula of C 4H10 reacts with chlorine, monochlorinated products can be formed. (i) What condition(s) is/are used for this reaction? [1] (ii) Write a balanced equation for the above reaction. [1] ACJC 2009 8872/02/Aug/09 Preliminary Examination

4 (iii) Draw the displayed formula of all the possible monochlorinated products formed. [4] (b) Define the term standard enthalpy change of combustion. [1] (c) (i) Write an equation to show how butane, C 4H10, burns in excess oxygen. [1] (ii) Use this equation and the following data to calculate the standard enthalpy change of combustion for butane. Enthalpy change of formation of CO2(g) = –393.4 kJ mol-1 Enthalpy change of formation of H2O(l) = –285.8 kJ mol-1 Enthalpy change of formation of C4H10(g) = –125 kJ mol-1 [2] [10 marks] ACJC 2009 8872/02/Aug/09 Preliminary Examination

5 3 (a) The following data apply to the compounds DClx and ECly. Compound Melting Point (°C) Boiling Point (°C) Solubility in water (g per 100cm3) DClx 714 1412 54.3 ECly -22.6 76.8 0.08 (i) Explain in terms of structure and bonding the differences in volatility for DClx and ECly. [3] (ii) Given that a solution of pH ≈ 6 is obtained when DCl x is dissolved in water, deduce the identity of DClx and write a balanced equation to explain how an aqueous solution of pH ≈ 6 is obtained. [2] ACJC 2009 8872/02/Aug/09 Preliminary Examination

6 (b) The hydrolysis of the ester, ethyl ethanoate, with sodium hydroxide requires the action of heat. CH3COOCH2CH3 + NaOH CH3COONa + CH3CH2OH (i) Describe, and explain in molecular terms, how the rate of the reaction is affected by a decrease in temperature. [3] (ii) The above reaction is a second order reaction. Explain what the phrase in italics means. [1] (iii) What is the effect on the rate of this reaction if a given volume of the reaction mixture is diluted with an equal amount of solvent? [1] [10 marks] 4 Describe a chemical test by which you could distinguish the following pairs of organic compounds. You should state the reagents and conditions, observations and write balanced equations. (a) (i) CHOH3CH2C CH2CHOC H3 [2] ACJC 2009 8872/02/Aug/09 Preliminary Examination

7 (ii) COOCH2CH3 OCOCH2CH3 [3] (b) With reference to the reaction scheme shown below, draw the structures of compounds A to C . State the reagents and conditions required to bring about steps 1 and 2 as labeled in the reaction scheme. [10 marks] CH3 Cl2uv KMnO 4 / H + heat CH3CH2OH heat, conc H 2SO 4 LiAlH 4 in dry ether CH2OH PCl 5 CH 2NH2 CH 2CN CH2COO _ A B C step 1 step 2 step 3 KCN in ethanol heat 2 [5] Step 1: Step 2: A: B: C: [10 marks] ACJC 2009 8872/02/Aug/09 Preliminary Examination

8 Section B Answer two of the three questions in this section on separate paper 1 (a) In the Haber process ammonia is manufactured from its elements. The highest equilibrium yield of ammonia in the Haber process should occur at a high pressure and at a low temperature. In practice, however these conditions are not used. (i) Write a balanced equation for the Haber process and state whether it is endo- or exo-thermic [2] (ii) What are the three usual operating conditions of the Haber process? [2] (iii) What factors other than Le Chatelier’s principle affect this choice? [2] (iv) Predict what would happen to the position of equilibrium if the operating temperature was changed to 1000K. Why? [2] (v) How will the yield of ammonia be affected if the reactant gases were passed through a tower packed with lumps of a more efficient catalyst? Explain. [2] A mixture containing equal number of moles of the reactant gases was heated to T K and P atm. The equilibrium mixture was found to contain the following concent